This invention relates to handheld calculators, and more particularly to an interface for reformatting calculator display signals so that they are suitable for display on a television.
Electronic calculators have become an essential tool for everyone. Consumers have a wide choice of calculator types and models.
Many persons own relatively inexpensive scientific calculators with one or two line displays, but recently more and more persons are discovering the advantages of xe2x80x9cbig-screenxe2x80x9d calculators characterized by a two-dimensional display screen capable of displaying graphs and other graphical images. These calculators are often called xe2x80x9cgraphing calculatorsxe2x80x9d because the popularity of these calculators for use in teaching various types of graphs and plots.
Calculators with these larger display screens are especially popular for educational applications. When these calculators are used in a classroom, it is often desired to duplicate the calculator display on an even larger screen suitable for viewing by an entire room full of students. The conventional approach is to use an overhead projector for such displays.
One aspect of the invention is an interface that receives display data input from a calculator and outputs a video signal, for use by a video device such as a television. A programmable logic device, such as an FPGA, receives the display data from the calculator, and delivers at least a portion of the data to a processor for use in determining the type of display format used by the calculator. The processor makes this determination and responds with data to the logic device to determine the processing to be performed by the logic device. The logic device might be comprised of different units for processing different formats, or it might be reprogrammed for each new type of format. In the former case, the appropriate unit is selected; in the latter case, the logic device is reprogrammed.
The logic device is further operable to perform hard logic processing of the display data, and the processor is further operable to receive partially processed display data from the logic device and to perform software processing of the display data. The division of tasks between hard logic processing and software processing is determined at least in part by the type of display format, and the xe2x80x9cprocessingxe2x80x9d performed by the logic device may be as simple as routing and/or buffering tasks.
As an example of task division between the logic device and the processor, for pixel type input data, the logic device can be used to multiplex the data and to provide appropriate control signals. On the other hand, for command type input data, the logic device might simply re-route the commands to the processor, or it might assist the processor by partially interpreting the commands. After processing, the processor outputs data having a format suitable for display by the video device.
In other embodiments, the logic device rather than the processor could be used to identify the type of display format used by the calculator.
An advantage of the interface is that it is useful with different types of calculators having different display formats. In the past, a different interface was required for each type of format. The invention provides a universal and upgradable interface that solves this problem. It is also designed to accommodate future calculators having new types of display formats.